[...]Should I use -hh -l wavpack options if I have the time for the encoding ?

If enconding time is not an issue for you I'd strongly suggest to consider the "-x" switch too:

QUOTE

-x[n] = extra encode processing (optional n = 1-6, 1 = default)

Like pre-4.0 versions of WavPack (and many other compressors), WavPack 4.60 normally works "symmetrically" in that encoding and decoding operate at about the same rate (regardless of the mode used). However, WavPack has an option to work "asymmetrically", so that extra processing can be done during encoding to provide better compression, but with NO corresponding cost to decoding performance!

This is enabled with the -x option and provides an average improvement in CD music compression of about 1% in "fast" mode, about 0.5% in the normal mode, and still less in the higher modes. Because the standard compression parameters are optimized for "normal" CD music audio, this option works best with "non-standard" audio (synthesized sounds, non-standard sampling rates, etc.) where it can often achieve enormous gains. The default level (n=1) provides a decent improvement with little cost in encoding speed and is recommended for all but the most time critical encoding. Higher levels provide some marginal improvement with an increasing cost of encoding speed. The highest levels (n = 4-6) are extremely slow but can provide significant improvement in special situations (i.e. synthesized sounds).